The subject matter disclosed herein relates to the management of backspin for an electric submersible pump (ESP), and more specifically to the management of backspin for an ESP in oil and gas applications with an electric motor.
In typical oil and gas drilling applications a well bore is drilled to reach a reservoir. The well bore may include multiple changes in direction and may have sections that are vertical, slanted, or horizontal. A well bore casing is inserted into the well bore to provide structure and support for the well bore. The oil, gas, or other fluid deposit is then pumped out of the reservoir, through the well bore casing, and to the surface, where it is collected. One way to pump the fluid from the reservoir to the surface is with an electrical submersible pump (ESP), which is driven by an electric motor (e.g., a permanent magnet motor, induction motor) in the well bore casing. Typically, a power source at the surface provides power to the electric motor via a cable. A magnetic field associated with a permanent magnet motor remains even when the permanent magnet motor is not actively driven. Additionally, some circumstances, such as a descending fluid column relative to or through the ESP, can lead to generation of voltage on the cable that otherwise provides power to the electric motor. This is referred to in the industry as motor backspin. Motor backspin may occur with induction motors, or more commonly with permanent magnet motors. By way of Faraday's law of induction, backspin of the permanent magnet motor may generate a voltage on the cable even when the permanent magnet motor is not actively driven.